The present invention relates to stringed musical instruments having finger boards including frets, and relates particularly to intonation of such a musical instrument by adjusting the positions of the open strings in order to improve the ability of the instrument to produce musical notes as accurately as practical throughout the entire designed tonal range of each string.
Stringed instruments such as lutes, guitars, banjos, and mandolins have several strings extending parallel with one another and held in tension, extending between two fixed supports, a nut at an outer end of a neck and a bridge mounted on a body from which the neck extends. The distance between the nut and the bridge is the open length of a string and thus establishes its fundamental tone when the string is placed in tension. A fingerboard including frets is included in the neck, so that a string can be made to sound a note higher than its fundamental tone by fretting the string, that is, by pressing the string against the neck adjacent to one of the frets.
Several factors contribute to determine whether a fretted string will produce the desired note. The material of which the string is made, the action height of the instrument (the distance between an open string and the frets), the thickness, or gauge, of the string, the tension of the string when it is tuned to its intended fundamental tone, and the length of the open string all affect the accuracy of the tone produced when the string is pressed against a fret that is located accurately on the fingerboard. Even the structure of the body of the instrument has an effect, since the top of the body is effectively a sound board that vibrates and thus may make a string vibrate as if it were a little longer than the actual distance between the nut and the bridge saddle.
While various adjustable guitar bridges and nuts are known, they present a non-traditional, technical, appearance that detracts from the traditional appearance of a guitar or other acoustic stringed instrument. What is desired, then, is a stringed instrument including the capacity for its intonation to be optimized string-by-string, yet having a traditional, non-mechanical appearance.